(1) Field of the Invention
The present invention relates to an optical beam scanning device, and more particularly to an optical beam scanning device in which a deflecting mirror is rotated to two-dimensionally scan a light beam, thereby projecting and displaying images on a screen or the like.
(2) Description of the Related Arts
In these years, there is proposed an optical beam scanning device (or a scanning image display device) in which a deflecting unit two-dimensionally deflects a light beam emitted from a light source to scan the light beam on a screen and a two-dimensional image is projected and displayed on the screen due to the afterglow effect of the light beam. In such an optical beam scanning device, a rotary mirror deflection device such as a galvano mirror or a MEMS (Micro Electro-Mechanical Systems) mirror is used for a deflecting unit that two-dimensionally deflects a light beam emitted from a light source.
However, in the case where such a rotary mirror deflection device is used to two-dimensionally deflect a light beam, a problem arises in that a slope error occurs in horizontal and vertical scanning directions due to the combination of a rotation angle (a deflection angle) in the horizontal direction and a rotation angle (a deflection angle) in the vertical direction, consequently causing distortion in a two-dimensional image displayed on a screen. Namely, in the optical beam scanning device using the rotary mirror deflection device, a technique that excellently corrects the distortion of a two-dimensional image in association with light beam scanning is necessary in order to display two-dimensional images in high quality.
For example, Japanese Patent Application Laid-Open Publication No. 2006-178346 discloses an optical scanning device for correcting image distortion, including a deflecting unit that deflects a light beam bundle emitted from a light source unit in a first scanning direction and a second scanning direction orthogonal to the first scanning direction, and a scanning optical system that guides the deflected light beam bundle to a scan surface. The deflecting unit includes a deflector that operates on sine waves in the first scanning direction. A single optical surface constituting the scanning optical system has a shape in which a second-order derivative in the first scanning direction changes in a direction in which the deflected light beam bundle diverges from the center to the rim in the first scanning direction, and the shapes are arranged in the second scanning direction.